The objective of the study was to obtain a clearer understanding of the concept of mental toughness as applied to a sport context. To do so, interviews were conducted with ten university-level Francophone Quebec athletes. The data analysis was conducted by following the principles of the abridged grounded theory. The results are in general agreement with the scientific literature as mental toughness was made up of interrelated basic characteristics such as internalized motivation, self-confidence, maturity and determination. Mental toughness was solicited when the athlete faced difficult situations such as adversity, but also when the context the athletes faced was free from complications (e.g. during training or victory). In the two classes of situations, adversity and freedom from adversity, mentally tough athletes exhibited a tridimensional reaction mode (cognitive, affective and behavioural dimensions) characterized by a management and control of attention, optimistic interpretation, activation control and body language control, consciousness, management of emotions and resilience. Contrary to the existing literature, the results suggest that mental toughness would not necessarily be linked to athletes performing at the top of their game; it would instead be connected to the capacity of athletes to produce good performances relative to their individual potential. This study can be viewed as a first step in the development of an instrument that would permit the evaluation of the level of mental toughness in Francophone athletes.